How can I deal with the overwhelming anxiety and sorrow that has afflicted me due to tooth decay, and what is the way to overcome feelings of guilt and despair, especially with my marriage approaching?

If a calamity befalls a servant and he endures it with patience, the reward for his patience will be greater, for "the patient will be given their reward without account." And if a calamity befalls them, they say, "Indeed we belong to Allah, and indeed to Him we return." Those are the ones upon whom are blessings from their Lord and mercy, and it is they who are guided. No calamity strikes except by permission of Allah. And whoever believes in Allah - He will guide his heart. So, the servant must be patient with Allah's decree and judgment, and know that the matter is easy, and that seeking help from doctors and beneficial medicines is part of the treatment commanded by the Prophet (peace be upon him).